Phoenix cluster sets record pace at forming stars

Aug 15, 2012

(Phys.org) -- Astronomers have found an extraordinary galaxy cluster -- one of the largest objects in the Universe -- that is breaking several important cosmic records. Observations of this cluster, known as the Phoenix Cluster, with NASA's Chandra X-ray Observatory, the NSFs South Pole Telescope and eight other world-class observatories, may force astronomers to rethink how these colossal structures, and the galaxies that inhabit them, evolve.

Stars are forming in the Phoenix Cluster at the highest rate ever observed for the middle of a galaxy cluster. The object is also the most powerful producer of X-rays of any known cluster, and among the most massive of clusters. The data also suggest that the rate of hot gas cooling in the central regions of the cluster is the largest ever observed.

This galaxy cluster has been dubbed the "Phoenix Cluster" because it is located in the constellation of the Phoenix, and because of its remarkable properties. The cluster is located about 5.7 billion light years from Earth.

"The mythology of the Phoenix -- a bird rising from the dead -- is a great way to describe this revived object," said Michael McDonald, a Hubble Fellow in the Kavli Institute for Astrophysics and Space Research at the Massachusetts Institute of Technology and the lead author of a paper appearing in the August 16th issue of the journal Nature. "While galaxies at the center of most clusters may have been dormant for billions of years, the central galaxy in this cluster seems to have come back to life with a new burst of star formation."

This video is not supported by your browser at this time.

This animation shows how large numbers of stars form in the Phoenix Cluster. It begins by showing several galaxies in the cluster and hot gas (in red). This hot gas contains more normal matter than all of the galaxies in the cluster combined, and can only be detected with X-ray telescopes like Chandra. The camera then flies in towards the large elliptical galaxy at the center of the cluster. The hot gas near this galaxy is giving off copious amounts of X-rays and cooling quickly over time, as shown by the change to a blue color. This cooling causes gas to flow inwards along filaments and form huge numbers of stars when it continues to cool. Credit: NASA/CXC/A. Hobart

Like other galaxy clusters, Phoenix contains a vast reservoir of hot gas -- containing more normal matter than all of the galaxies in the cluster combined -- that can only be detected with X-ray telescopes like Chandra. The prevailing wisdom had once been that this hot gas should cool over time and sink to the galaxy at the center of the cluster, forming huge numbers of stars.

However, most galaxy clusters have formed very few stars over the last few billion years. Astronomers think that the supermassive black hole in the central galaxy of clusters pumps energy into the system, preventing cooling of gas from causing a burst of star formation.

The famous Perseus Cluster is an example of a black hole bellowing out energy and preventing the gas from cooling to form stars at a high rate. Repeated outbursts from the black hole in the center of Perseus, in the form of powerful jets, created giant cavities and produced sound waves with an incredibly deep B-flat note 57 octaves below middle C.

"We thought that these very deep sounds might be found in galaxy clusters everywhere," said co-author Ryan Foley, a Clay Fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "The Phoenix Cluster is showing us this is not the case - or at least there are times the music stops. Jets from the giant black hole at the center of a cluster are apparently not powerful enough to prevent the cluster gas from cooling.

With its black hole not producing powerful enough jets, the center of the Phoenix Cluster is buzzing with stars that are forming about 20 times faster than in the Perseus cluster. This rate is the highest seen in the center of a galaxy cluster but not the highest seen anywhere in the Universe. However, the overall record-holding galaxies, located outside clusters, have rates only about twice as high.

Optical/UV/X-ray composite image of the Phoenix cluster, with a pull-out of the central region. (Credit: NASA/CXO Press Office)

The frenetic pace of star birth and cooling of gas in Phoenix are causing both the galaxy and the black hole to add mass very quickly -- an important phase that the researchers predict will be relatively short-lived.

"The galaxy and its black hole are undergoing unsustainable growth," said co-author Bradford Benson, a Kavli Fellow in the Kavli Institute for Cosmological Physics at the University of Chicago. "This growth spurt can't last longer than about a hundred million years, otherwise the galaxy and black hole would become much bigger than their counterparts in the nearby Universe."

Remarkably, the Phoenix Cluster and its central galaxy and supermassive black hole are already among the most massive known objects of their type.

Because of their tremendous size, galaxy clusters are crucial objects for studying cosmology and galaxy evolution and so finding one with such extreme properties like the Phoenix Cluster is important.

"This spectacular star burst is a very significant discovery because it suggests we have to rethink how the massive galaxies in the centers of clusters grow," said Martin Rees of Cambridge University, who was not involved with the study. "The cooling of hot gas might be a much more important source of stars than previously thought."

The Phoenix Cluster was originally detected by the National Science Foundation's South Pole Telescope, and later was observed in optical light by the Gemini Observatory in Chile as well as the Blanco 4-meter and Magellan telescopes, also in Chile. The hot gas and its rate of cooling were estimated from Chandra data. To measure the star formation rate in the Phoenix Cluster, several space-based telescopes were used including NASA's WISE and GALEX, and ESA's Herschel.

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User comments : 28

Am I understanding this correctly - these researchers are claiming to have positive proof that stars are currently being observed to be forming in this cluster?They can actually show us in a video how stars are popping up over a matter of weeks or months and we can actually see stars being born with our own eyes?Please correct me if I'm misunderstanding this.

Before astronomers try to "rethink", the must first learn to think. Where is all this cool gas coming from, and why is it concentrated near the center of the cluster??? Could it be because that is where the gas originated from??

tuxford, why not reveal WHERE and HOW laviolette gets his ideas?here are some paraphrases of works from tuxfords idol laviolette, it illustrates how based in reality his worldview really is.this is from a book he wrote."First time proof of the existence of interstellar radio signals of intelligent origin being sent to us.Evidence that pulsars are part of a vast network of ETI communication beacons.This exhaustive study presents first time proof that astronomers have been receiving radio signals of intelligent origin. As early as 1967 and continuing to the present, radio astronomers have been carefully studying and cataloging unusual interstellar beacons called pulsars thinking them to be stars of natural origin.Dr. LaViolette, who has been researching pulsars for 27 years, shows that, up to now, the nature of these radio sources has been grossly....

misunderstood. He has discovered that a number of very unique pulsars are nonrandomly distributed in the sky and mark key Galactic locatations that have particular significance from an ETI communication standpoint. He also presents evidence of unusual geometric alignments among pulsars and intriguing pulse period relationships. Equally compelling is the message they are sending-a warning about a past Galactic core explosion disaster that should help us avert a future global tragedy. Contains extensive analysis of pulsar data, revealing new ideas about the origins and functions of pulsars Provides proof of an extraterrestrial communication network Includes information about the formation of crop circles and force-field-beaming technolgy."

hmmmm, crop circles, force field beaming, et communication codes hidden in the stars revealing this all to laviolette......SCIENCE FICTION IS WHAT LAVIOLETTE IS TUXFORD!!! GIVE IT A BREAK ALREADY!

This is one of those "Duh!" moments. How is the gas cooling near (but well outside) the central galaxy? We see this cooling as X-rays, but what causes the X-rays?

How about dark matter? Possible, but let's stick with DM as dark. What about neutrinos? On THIS scale neutrinos do interact with the gas. If the neutrinos are gravitationally bound to the cluster, they could be the source of the cooling. Due to neutrino oscillation, the effective mass of the neutrinos will be due to the time spent as each neutrino variant.

Oh, and there is an experiment I'd love to try, but I think it is current well beyond the practical. Produce two neutrino beams at high energy, overlap them in opposite directions, and look for photons and other particles from the collisions. We know that the interaction of neutrinos with ordinary matter is extremely low, but neutrinos with neutrinos may be very high.

If it is, the neutrinos should be excellent coolers in this situation.

No one claims that an animation is depicting the observations, or that the time scales of star formation is weeks. Star formation takes some thousands of years at the end of a molecular cloud collapse, and yes these clouds and the various stages are observed as we have many samples.

Dunno what the star formation rate here is, but Milky Way is observed to form ~ 1 star/year.

Maybe it is truly ignorance in this one case. But instead of just asking, we get the trolling.

They can actually show us in a video how stars are popping up over a matter of weeks or months and we can actually see stars being born with our own eyes?

I'll bet they have an equal number of videos as every creationist put together has of God creating men.

The difference is the scientists actually have these things called facts, reason, and observations to offer as evidence. People can (and do!) debate what these observations/facts mean, but they are there for everyone to see in the exact same way.

Creationists have dozens of books written over thousands of years in several languages, mistranslated by who knows how many people, selectively added and subtracted from seemingly at random by various people in power, and written in a purposefully vague way.

I know science isn't as easy to understand as saying "God did it" but that doesn't make it any less accurate.

The central galaxy in the Phoenix cluster (aka SPT-CLJ2344-4243) is quite a remarkable object. This galaxy appears as an extreme example of an ultraluminous infrared galaxy(ULIRG), exhibiting a heavily obscured starburst region and a central AGN.

And what a starburst! Complex star-forming filaments are observed up to 70 kpc from the galaxy's center and the total star formation rate for the systems is estimated at over 700 Msun/yr. It's estimated that ~20% of the cooling flow in the cluster is being converted to stars, a rate not seen in any known galaxy cluster. This type of star formation through accretion of the intercluster medium may turn out to be significant for massive galaxies near the center of clusters (as opposed to star formation through gravitational interactions or mergers between galaxies).

The galaxy cluster itself is an enormous assembly, with a diameter of 2.6 million parsecs (8.5 million l.y.) and a staggering estimated mass of 2.5x10^15 Msun.

"No one claims that an animation is depicting the observations, or that the time scales of star formation is weeks."

I am an atheist, and have a similar question. I have seen estimates of 5-6 stars forming annually in the Milky Way. Has anyone ever looked for one of them as it actually begins to emit enough light to be called a "star"? No matter how long it takes to form, there must be a moment when there was no star visible and now there is.

We have the technology to monitor huge numbers of objects over time. Maybe it's time to try to find a brand new star.

All the time, Google up "protostar". You can see many photos of them in various stages of development. The average of the new star creation in the Milky Way is about 1 to 2 a year. When you consider that there are hundreds of billions of stars in Milky Way, seeing one that is just "turning on" it difficult.

But don't let the "turn on" or "forming" or "born" distract you from the realization, that turning on, forming, born, is done over periods of many thousands of years. It doesn't do much in a span of 10, 100, 1000 or even several thousands of years.

They are born gradually, and die spectacularly. And as spectacular as they are, even seeing a supernova in real time is a challenge. You've got to get lucky, AND burn up a lot of computer time and some telescope time just watching.

They can actually show us in a video how stars are popping up over a matter of weeks or months and we can actually see stars being born with our own eyes?

Are you REALLY this stupid or are you just playing dumb for fun? Stars don't form over periods of weeks or months, they form due to slow coalescence of surrounding gasses over tens of thousands of years or longer...

You creationist idiots always like to ask for things that are impossible to show because you don't understand anything that you are talking about and then declare victory when scientist are unable to show the impossible. Can't show a dog turn into a frog via evolution? Evolution must be wrong...

It's just their fun little way of bragging that science rarely "proves" anything without realizing that the staggering amount of evidence would amount to proof beyond any reasonable doubt. Lucky for them, the various religious texts are ironclad in their accuracy. After all, they're each divine in nature. Except when proven wrong, then they're merely divinely inspired and the writer/prophet got mixed up.

I understand that star formation is a long process. Still, as far as I know, it seems logical to suppose that there must indeed be a moment when the first nuclear reaction happens and the star emitts its first light. "It is turned on", one is tempted to say.

Even so, there are many reasons why we can't have a video of a star being turned on:

-- a star just emitting first light will be faint enough,

-- plus, we can't have enough resolution to pinpoint and show it.

-- And also, we do not know where the telescope should be focused.

This probably depends on the distance, but I am guessing that a picture with enough resolution to show one protostar just emitting first light ("turned on") will be a very large file. Obviously, a video showing this will require many such large files.

Or, we may simply dont know enough yet to correctly perceive the process of a star "turned on".-.

The 'switch on' is the start of the reactions at the core. Even for our Sun, the energy released in the core takes thousands of years to reach the surface and to start the thermonuclear reaction, the star must have reached a comparable temperature through gravitational collapse anyway, there would probably be little external change to show when the reactions started over a useful time span unless you could monitor the neutrino flux.

I'm not positive about this, but I doubt it would go from zero luminosity to full luminosity all at once, it would probably gradually increase in brightness over a long period of time. So while you're right that there is a point when it starts emitting significant light, it's not like turning on a light bulb, more like turning a dimmer switch to brighten the bulb slowly over a long period of time... that would be very difficult to detect.

The reason photon pressure is dominant to counteract gravity is interesting by the way. It is because stars are opaque and dense, so photons are trapped. It takes, IIRC, many 100 000s year for a photon to bounce its way up to the surface! (By a random walk in 3D.) Hence photon density in a star is immense, hence its pressure is dominated by photons.

He clearly understands this better than I do; but if I'm getting the general meaning, Deathclock is right that a new star would be more like a dimmer. We may or may not see any visible light for the first several thousand years after the star begins fusion reactions. I'm a bit out of my depth here though, so please correct me if I'm understanding this wrong.

"We may or may not see any visible light for the first several thousand years after the star begins fusion reactions. I'm a bit out of my depth here though, so please correct me if I'm understanding this wrong."

No you are right on track, the gradual brightening as the fusion gets going,,, is so gradual (on human scales) that you could look at it today, and then look at it in 100 years and you wouldn't detect a measurable (with present technology) difference in the two observations.

Right, we are like bullets in flight, we live our entire lives in the blink of an eye compared to astronomical events. The study of astronomy is basically the study of a freeze-frame of a highly complex dynamic system.

Sub: cosmology structure-Cosmic FunctionThe subject of Cosmology needs best of brains trust. The origins-Cosmology Vedas- must be researched in-depth that requires East West Interaction.The outlines are given in my Research Paperhttp://www.scribd...Dec-1999More details are given in Cosmology Structures new modeling- Carnegie Centennary Symposium- 3, author V Nanduri, Jan 2003.The Cosmic function of the Universe must be understood with Comprehension and Distribution of Energy through Cluster-Galaxies.universe Model include 10^9 LY and Multi -universe is part of Cosmoshttp://vidyardhic...ion.html

@ Q-Star (& anyone else who is unfamiliar with this 'vid' poster): I'd be careful about taking vidunmaya seriously. Every so often they will make some kind of statement like that; you can't exactly tell where the religious elements end and where any 'physics' is supposed to start. Judging by the strange and repetitious nature of their occasional postings, I have a strong tendency to judge them as being a troll. Judging by vid's activity page, so does everybody else. Cheers, DH66

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